Surgical cutting instrument having electrically heated cutting edge

ABSTRACT

A surgical cutting instrument includes an electrically heated cutting edge and a power supply system for maintaining the cutting edge at a constant high temperature for sterilizing the blade, cutting tissue, and cauterizing the incised tissue to reduce hemorrhage from the cut surfaces of the tissues (hemostasis). .Iadd.

RELATED APPLICATION

This application is a reissue of Pat. 3,768,482 which matured fromapplication 295,879 filed October 10, 1972 and which is a continuationof continuation-in-part of U.S. Pat. Application Ser. No. 63,645 filedAugust 13, 1970, now abandoned, which is a continuation of U.S. Pat.Application Ser. No. 681,737 filed Nov. 9, 1967, now abandoned..Iaddend.

The control of bleeding during surgery accounts for a major portion ofthe total time involved in an operation. The bleeding that occurs whentissue is incised obscures the surgeon's vision, reduces his precisionand often dictates slow and elaborate procedures in surgical operations.Each bleeding vessel must be grasped in pincer-like clamps to stop theflow of blood and the tissue and vessel within each clamp must then betied with pieces of fine thread. These ligated masses of tissue die anddecompose and thus tend to retard healing and promote infection.

SUMMARY OF THE INVENTION

Accordingly, the present invention provides a surgical cuttinginstrument having a cutting edge which is electrically heated to aconstant high temperature for sterilizing the blade, cutting the tissueand cauterizing the surfaces of the incision, thereby allowing surgeryto be more rapidly performed. This is accomplished in accordance withthe illustrated embodiment of this invention by providing electricallyheated elements disposed to form the cutting edge of the blade and byproviding a common constant voltage source which operates to maintainthe cutting edge at a high substantially constant temperature during itsuse. The hot cutting edge according to the present invention decreasesthe amount of tissue that is damaged and reduces the tendency of theinstrument to stick to the heated tissue in the incision. In oneembodiment, the material used in the electrically heated cutting edgehas a positive temperature coefficient of resistance. The temperature atwhich the cutting edge of the blade is maintained depends upon suchfactors as the nature of the tissue to be cut, the speed of cuttingdesired, the degree of tissue coagulation desired, and the non-adherenceof the blade to the incised tissue and generally is maintained between300°-1,000° Centigrade for typical incisions in typical human tissue.The cutting edge includes many parallel current paths in a conductivematerial connected between the terminals of a constant-voltage powersource. The operating temperature of the cutting edge is controlled byaltering the voltage between the terminals.

The handle of the cutting instrument is thermally insulated from theblade to permit comfortable use of the instrument and the handle andblade with its electrically-heated cutting edge are detachable for easyreplacement and interchangeability with blades having cutting edges ofvarious shapes and sizes determined by the nature of the incision to bemade and the tissue to be cut.

DESCRIPTiON OF THE DRAWINGS

FIGS. 1 and 2 are pictorial views of embodiments of cutting instrumentsaccording to the present invention; and

FIG. 3 is an end sectional view of the embodiment of FIG. 1 showing theheater element disposed as the cutting edge of the blade betweenelectrodes on opposite sides thereof.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to FIGS. 1 and 3 of the drawing, there is shown thesurgical cutting instrument 9 including a thin ceramic card 63 in thedesired shape of a surgical cutting blade which is detachable from thehandle or holder 10. An electrical heating element 61 is disposed in theregion of, i.e. on or about, the cutting edge 62 of ceramic card 63between electrodes 65 and 67 which are electrically connected to aconstant voltage source through the cable 14 and the connectors 71 and73. The element 61 may be a continuous conductive film attached to thecard 63, for example, using conventional vapor-deposition processes. Thematerial used for the element 61 may be tantalum nitride or othersimilar material having a positive temperature coefficient ofresistance. Thus, as a portion of the element cools when in contact withtissue, the resistance of such portion of the element decreases anddraws increased current from the constant voltage source 75. Thislocalizes the portion of the element 61 in which additional power isdissipated to the portion cooled on contact with tissue. The temperatureof such portions of the element may thus be maintained substantiallyconstant as the cutting edge comes in contact with tissue being cut.Other suitable materials having positive temperature coefficients ofresistance for use as the element 61 include tungsten, nickel, platinum,chromium, alloys of such metals, and the like.

In the embodiment of the present invention illustrated in FIGS. 1 and 3,the heating element 61 is laterally disposed across the cutting edge 62of the blade-like support card 63 to form a continuum ofcurrent-conducting paths along the length of the cutting edge. Thesecurrent-conducting paths of heating element 61 are allparallel-connected between the contact electrodes 65 and 67 and whichare disposed on opposite sides of the support card 63. These contactelectrodes may be formed of a material such as platinum or tungsten, orthe like, which makes good contact with the heating element material andwhich does not readily oxidize at elevated operating temperatures.Alternatively, the heating element 61 may also be arranged to traversethe cutting edge 62 as discrete, closely-spaced elements 69 that are allparallel-connected between opposite-side electrodes 65 and 67 on thecard 63, as shown in FIG. 2. Such discrete elements are connected on oneside of the card 63 to the electrode 67 and on the other side of thecard to electrode 65. In the limit, the heating elements 69, as shown inFIG. 2, may be sufficiently closely located along the cutting edge 62 inparallel connection between the opposite-side electrodes 65 and 67, asto perform substantially as a continuous conductive film, as shown inFIG. 1.

In each of the illustrated embodiments, the electrodes 65 and 67 andheating elements 61 or 69 may be conductive material which isvapor-deposited in the desired interconnected patterns on a suitableelectrically-insulating ceramic card 63. Alternatively, the electrodesand heater elements may be etched to shape on a card 63 whose sidesurfaces and edges are coated with the selected conductive materials.

In each of these embodiments, the electrodes 65, 67 are connectedthrough conductors 14 and suitable electrical connectors 71, 73 mountedin the handle 10 to a source 75 of substantially constant voltage. Thissource 75 may be a conventional, well-regulated power supply or otherlow-output impedance supply which is capable of delivering the totalcurrent required by all portions of heating element 61 (or by alldiscrete elements 69) while maintaining the voltage between electrodes65 and 67 substantially constant. In this way, each portion of heatingelement 61 (or discrete element 69) which cools down when placed incontact with tissue during surgical use decreases in resistance betweenelectrodes (for positive temperature coefficient of resistance). Withconstant voltage applied to the electrodes, the cooled regions drawcorrespondingly more current and dissipate more power in the cooledregion, thereby tending to maintain the heating element all along thecutting edge at the preselected operating temperature. The operatingtemperature of the cutting edge is thus selected by altering the valueof the constant voltage supplied by source 75. To assure substantiallyuniform operating temperature over the length of the cutting edge 62,the heating element 61 (or the discrete elements 69 closely spaced aboutthe edge) may have substantially uniform resistance per unit area. Theceramic card 63 may be formed of high thermal conductivity material suchas aluminum oxide, or the like, to assure more uniform operatingtemperature along the length of the cutting edge.

I claim:
 1. A surgical instrument for cutting tissue with simultaneoushemostasis, the instrument comprising:insulating support means having.Iadd.as a portion thereof .Iaddend.a tissue-cutting edge .[.andincluding thereon.]. .Iadd.region and including in physical contact withsaid support means .Iaddend.an electrically-heatable element ofelectrically-conductive material disposed on said edge region defining acutting edge to contact tissue and to conduct electrical current along aplurality of parallel current paths for directly heating the cuttingedge in response to electrical signal applied thereto; and connectionmeans on said instrument providing electrical connections to saidelement for supplying electrical signal thereto to be conducted along aplurality of parallel current paths.
 2. A surgical instrument as inclaim 1 wherein said electrically-heatable element includes asubstantially continuous conductive layer disposed adjacent the cuttingedge; andsaid connection means includes a pair of electrodes which aredisposed in spaced relationship on opposite sides of said support meansand which are connected to said conductive layer on opposite sides ofthe cutting edge for conducting current along a plurality of parallelcurrent paths oriented substantially laterally across the cutting edge.3. A surgical instrument as in claim 1 wherein:.[.said.]. electrodes aredisposed on opposite sides of said support means; and theelectrically-heatable element includes a plurality of discreteelectrically-heatable elements disposed to traverse the cutting edge.[.of said support means.]. and connected at the ends thereof toelectrodes on opposite sides of said support means.
 4. A surgicalinstrument as in claim 1 wherein:said electrically-heatable element onsaid support means is formed of electrically-conductive material whichhas positive-temperature coefficient of resistance; and said connectionmeans includes a source of substantially constant voltage connected to.[.said pair of.]. electrodes for maintaining the voltage across theelement substantially constant as portions of said element contacttissue. .Iadd.5. A hemostatic surgical cutting blade comprising: acutting blade having a tissue cutting edge; an electrically heatableelement of electrically conductive material thermally connected to andat least extending along the area of the cutting edge such that saidedge may be maintained within a predetermined temperature range; and twoor more electrodes disposed in spaced relationship on the cutting bladeand connected to said electrically conductive material for conductingcurrent along a plurality of parallel current paths. .Iaddend..Iadd. 6.The hemostatic surgical cutting blade claimed in claim 5 wherein saidelectrodes are disposd in lateral spacial relationship on opposite sidesof said cutting edge for conducting current along a plurality ofparallel current paths oriented substantially laterally across thecutting edge. .Iaddend..Iadd.
 7. The hemostatic surgical cutting bladeclaimed in claim 5 wherein said electrically heatable element is furtherdefined as comprising a plurality of discrete electrically heatableelements. .Iaddend..Iadd.
 8. The hemostatic surgical cutting bladeclaimed in claim 5 wherein said electrically heatable element is formedfrom a material having a positive-temperature coefficient. .Iaddend..Iadd.
 9. The method of cutting tissue with simultaneous hemostasiscomprising the steps of: contacting the tissue to be cut with a tissuecutting edge at an elevated temperature; establishing the elevatedtemperature by conducting current along a plurality of substantiallyparallel current paths located along said tissue cutting edge; andincreasing power dissipation in regions of the edge which areselectively cooled upon contact with tissue for maintaining thetemperature of the edge within a selected range. .Iaddend..Iadd.
 10. Amethod of cutting tissue with simultaneous hemostasis comprising:conducting current along a plurality of substantially parallel currentpaths oriented laterally across a supported tissue cutting edge;dissipating power in regions of said tissue cutting edge responsive toselective cooling of said regions by reason of contact with tissue;thereby maintaining said tissue cutting edge at a selected temperaturerange. .Iaddend..Iadd.
 11. A method of hemostatic surgery as in claim 9wherein: current is conducted along a plurality of substantiallyparallel current paths which are discrete. .Iaddend..Iadd.
 12. A methodof hemostatic surgery according to claim 9 wherein: the resistance ofthe parallel current paths increases with increasing temperaturethereof. .Iaddend..Iadd.
 13. A method of hemostatic surgery according toclaim 12 wherein: a constant voltage is impressed upon the currentpaths. .Iaddend.